Nanoscale materials are currently being exploited as active components in a wide range of technological applications in different fields, such as composite materials, chemical sensing, biomedicine, optoelectronics and nanoelectronics. Many recent efforts have focused on the creation of various nanostructures including spheres, tubes, cables, sheets and, especially, wires, have been successfully synthesized, since these nanoscale building blocks are anticipated to transform the semiconductor industry.1-2 However, the realization of practical nanodevices requires that these nanostructures be integrated efficiently and economically into various intricate architectures. Synthetic control from bottom-up approach of one-dimensional (1D) nanostructures into complex heterostructures would impact the design of future electronic devices by simplifying much of the processing associated with nanodevice fabrications.Among the various semiconductors, silicon carbide (SiC) is an important group IV-IV compound that possesses unique physical and electronic properties. SiC-based electronics will be better than silicon-based devices in certain applications, because they can operate at higher temperature, higher power, and higher frequency as well as withstand harsh environments but with reduced cooling requirements. Our previous results demonstrated that SiC nanocones and heterostructures can be created by utilizing iron nanoparticles, that are originally encapsulated in a graphite-like shell, to catalyze a vapor-solid reaction between carbon and silicon monoxide vapor. Herein, we present that crystalline SiC Y-junctions can be formed by the coalescence of Fe catalysts, which have already catalyzed the formation of a single SiC nanowire creating a SiC Yjunction with either parallel or inclined branches.Two kinds of crystalline SiC Y junctions have been observed, from the systematic TEM observation, to show either two inclined branches or parallel branches. This variation in branching corresponds to the branch growth direction mismatch and growth without direction mismatching. Noting that the catalyst droplets are located at the tip of the stems, the branches must form prior to the stems. Therefore, the formations of the crystalline SiC Y junctions are attributed to the coalescence of two catalyst droplets that have already each formed a SiC nanowire branch, while the merged catalyst remains catalytically active and catalyzes the stem formation. Moreover, "V"-shaped SiC nanostructures are detected in the products, in which the catalyst is located at the intersection between two branches, which supports the catalyst droplets coalescence mechanism, as shown in Fig. 1. The crystalline SiC Y junction formed by the coalescence of two parallel branches follows the original <111> SiC growth direction. The merged catalyst yields a shared planar interface and creates a single crystal stem. However, for the crystalline SiC Y-junction formed by the coalescence of two inclined branches, the interface between the merged catalyst and stem is fac...